A press release issued today says the Amore Bay line of hot tubs is "just what the love doctor ordered."

Dimension One spas points to research showing that warm contact and frequent hugs up women's oxytocin levels, increasing bonding and trust between people. This is all true, and taking a soothing warm bath together seems a very likely way to promote the oxytocin release.

According to the press release,

Some researchers have also suggested a beneficial link between oxytocin and social anxiety, memory control, cardiovascular functions, and thermoregulation in menopausal women. This must be what they meant by 'sexual healing!'

As the name implies, these hot tubs really are built for amore.

With curvaceous lines, strategically placed water jets, mood lighting, a "playground" area, a hand held massager and cup holders, the only thing left to do is download Barry White or Marvin Gaye on the Amore Bay's wireless, IPOD friendly stereo!

It's interesting that, unlike the 1970s image of hot tubs as places for wild partying, Dimension One is marketing this to couples as a way to improve not only the sexual relationship but also trust and comfort.

Kudos, I say, to this company for a press release that doesn't twist the science, but speaks to our fascination with neuroscience and drive to connect with humor and humanity.

Scientists seem to have a good handle on the neurochemical basis of maternal behavior in mammals -- including the human variety. Mothering behavior is based on a combination of prolactin, which stimulates milk letdown and nursing behavior, oxytocin, which stimulates labor, the release of milk from the breasts and, along with dopamine, the bond with the baby.

But fatherhood remains a mystery. Vasopressin, the hormone that's almost a twin to oxytocin and more important to the male brain, seems to be involved. Oxytocin also is likely involved in male bonding to mate and offspring. And prolactin, often thought of as a female hormone because of the connection to nursing, turns out to be quite important, as well.

This 2003 study of monkey fathers sheds some light on prolactin's role.

Researchers Carsten Schradin, Deann Reeder, Sally Mendoza and Gustl Anzenberger tracked the prolactin levels in the urine of the coppery titi (Callicebus cupreus), the common marmoset (C. jacchus) and Goeldi's monkey (C. goeldii). These three species of monkeys are monogamous, and the male contributes a great deal to the care of the young, especially by keeping the baby safe and close by carrying it. In non-monogamous species, the mother and sometimes siblings and related adult females do all the carrying.

If the hormone prolactin, which stimulates maternal behavior in mammals, does the same thing for furry dads, you would expect changed in prolactin levels to correlate with the periods when fathers begin to carry babies. Moreover, you'd expect unmated males to have lower levels than fathers. Finally, if the increased prolactin was the result of tactile stimulation of that warm little body clinging to the father's back, the fathers that spent the most time carrying would have the highest levels.

These three species of monkey make for a neat comparison, because, while the males all invest in their offspring by carrying the relatively helpless babies on their backs, they don’t put in equal time.

The titi father does almost all the infant hauling. Titi monkeys live in small family groups, a monogamous pair and one to three offspring. In this species, the male is the primary caregiver. Males pick up the infants soon after birth, and carry them 70 to 90 percent of the time until weaning, sometimes continuing until the birth of the next offspring. Siblings seldom lend a hand. The titi fathers did have higher prolactin levels than females and higher than their unmated sons, but they didn’t show a significant increase after the birth of infants

The marmoset males are the primary caregivers, but they get a bit more help from mother and siblings. Marmosets live in family groups headed by a monogamous mother/father pair. Mother, father and older offspring all help take care of the younger monkeys, carrying them around and sharing food with them, but the father is the primary caregiver.

In the marmosets in the study, mating and forming a pair bond didn’t increase prolactin levels; it began to rise shortly before the birth. Marmoset fathers had higher levels in the phase before they began carrying than their sons did.

Goeldi's monkeys also live in family groups and raise offspring cooperatively; Goeldi's typically have only one baby at a time. In this species, the mother starts out as the primary carrier. The fathers don’t start carrying the babies until about three weeks after birth. There was no difference in the urine levels of mated and unmated Goeldi's pre-pregnancy. The Goeldi's fathers, which don't begin to carry for three weeks, showed an increase in the hormone during the pre-carry period. Such an increase in prolactin immediately before the carrying stage could facilitate transition from nonparticipation to direct participation of the father in care-giving.

The experiment showed the first hypothesis, that prolactin levels are timed to paternal behavior, to be true, at least somewhat. The second, that fathers would have higher levels than non-breeders, also held true.

But the amount of carrying time didn't correlate with higher levels of prolactin. In other words, it's unlikely that the skin-on-skin contact stimulates the production of prolactin. So, the study shows a clear link between paternal behavior and prolactin, but not the mechanism.

When a son living in the family group becomes a breeder, the researchers think, the prolactin levels of marmosets and titi males goes up in preparation for their upcoming role as fathers. Maybe marmoset and titi dads don’t need priming prebirth because their levels are always higher. Sustained high levels of prolactin in these two species reflect the need to be continuously available to carry.

They don’t know exactly when prolactin levels increase in titi or jacchus, or what stimulates it, but in goeldie, one small study showed prolactin levels increased before birth and increased again after the birth.

They caution that carrying is not the whole story when it comes to parental investment in care. Goeldii fathers are immediately attracted by their infants, for example, and if a researcher hands the infant to its father, he will take it up. So other aspects of fathering may be influenced by other hormones or neurochemicals.

Michael Gurian is the author of a series of books that help parents and teachers understand the differences between boys and girls -- and how to use that understanding to raise healthy kids and help them learn. Gurian's work takes into account the latest findings from neuroscience and psychoneurobiology, for example, the way that estrogen and oxytocin in girls and testosterone in boys create changes in the brain at puberty. His latest book, "Nurture the Nature," will be published in May 2007. For info about his other books, see The Gurian Institute website.

At The Gurian Institute, teachers learn how to recognize the differences in individuals while devising appropriate classroom activities to address the different ways boys and girls learn.

Gurian (like me) comes from the feminist era of the 1970s, when we believed that differences between men and women were the result of societal expectations and conditioning. He is therefore very sensitive to the nuances and pitfalls of discussing biological differences between the sexes, and he does so with awareness of the diversity of individuals and the continuing need to struggle for social equality.

I spoke with Michael about how adolescent boys and girls can experience healthy relationships with each other.

HUG: The bodies of adolescent boys are surging with testosterone, while girls are experiencing the effects of estrogen and its enhancement of the effects of oxytocin. For those who haven’t had a chance to read your books, can you please briefly explain how these different hormones affect the brains, emotions and activities of each?

GURIAN: Boys tend toward aggression nurturance, a system based on competitiveness and helping each other move up hierarchies. When someone has a weakness, pointing it out and forcing the person to mitigate the weakness.

Girls tend to use empathy nurturance: "How are you, I'm going to hug you and make you feel better." Males will try to make you perform better.

Girls do become very aggressive in adolescence with verbal shaming and creating in-groups and out-groups, creating hierarchies. However it's not as physical. Boys are more physically aggressive, no doubt. Testosterone is not just a growth hormone, it's a sex and aggression chemical. So with 10 to 20 times more testosterone than a girl, and his system being based on this hormone, he will tend to be more physically aggressive.

They're both doing what each other are doing but in such different ways that people will say boys are more aggressive and girls are more nurturing. Girls have more of an intimacy imperative, and boys have more of a performance imperative, so this language can make sense, but I think the truth is that boys utilize more aggression nurturance and girls utilize more empathy nurturance. Both boys and girls nurture! But in their own ways.

HUG: Girls have a more intense need for connection at a time in their lives when they naturally start to become more independent from the family, and a time when parents often begin to look outward from the family. How does this affect teen-aged girls?

GURIAN: The intimacy imperative is so very strong, due to the estrogen, progesterone, oxytocin and serotonin interactions, that it creates such a strong need for intimacy and to develop the self through intimate relationship. Simultaneously, the psychology of human development is that children must separate from their parents.

Both males and females hormonally need each other and want connection. Teenage males in general tend to want more sex and less intimacy, and females tend to need more social intimacy. As she's trying to separate from mom and still has a deep need for intimacy, she will project a lot of it onto friends and males.

With boys, there will be romance and sexuality mixed in, which further complicates things. She's trying to bond with the boy and at same time trying to understand how to have a self. The malleability of her hormonal, social and emotional base often leads to her to nearly give up herself just to get intimacy. Often we will see a girl during the teen years fighting the urge to obtain intimacy at the expense of self. Part of her internal destiny is to see how to give a self without giving up a self. And she fights that fight with the male.

The males are smart. They'll say, "I love you, I love you," get the sex from her and never call her again. When a male has sex and orgasms, he gets that hit of oxytocin that takes him to a level similar to hers, so he will exacerbate the problem by saying, "I love you you're the best." His oxytocin goes down in a couple of hours, as testosterone floods in and mitigates the oxytocin level.

But she has this oxytocin that rages for days and days, and she thinks he's in love with her. I think that's why we have so much depression after these romantic and sexual breakups.

HUG: So, dating begins at a time in their lives when males and females are, chemically, at their most disparate. How can these very different organisms come together in a way that gives both what they need without getting them into damaging situations?

GURIAN: The most tried-and-true way throughout history, and one we must constant reinvigorate, is accountability to family and extended family. Always remember, this hormonal base and reproductive system was meant to be nurtured in a three-family system, and this boy and this girl are supposed to be accountable to this system and social network.

For an individual child, there may be certain times where dad or mom isn't around, or there is no extended family. In those cases, I would try to get the community and schools to focus on character development: going to synagogue, mosque, anything, especially for males. And sexuality needs to be part of that character development.

The point of having them accountable and loved in a three-family system is they get their emotional needs met in a variety of settings, so girls don't need to hyper-utilize the males. It's normal primate behavior. I don't think there's a tip a girl can follow to hold onto herself that's as powerful as making sure she's loved.

HUG: You say in your books you wouldn't let your daughters date until they were 16. Did you make that stick?

GURIAN: Yes, they're fine with that. Our kids have bought in. Our parenting model, is we're constantly in dialog with them. How's this working, how does it need to get modified? They'll suggest things, we go back and forth. I'm going to get another piercing now, one of my daughters will say, and we as parents need to buy into that, since this is a milestone.

For my daughters, we have asked them to set a goal o f not having intercourse until a guy has to be around for six months at least, and proven his love and fidelity. Teenagers will at some point start to have sex without parents' permission! But, if you want to be a smart young woman, we say to our 17-year-old, you want to see if he sticks around for six months. This seems to work for her for now, it seems to give her safety and security.

HUG: This presupposes that a girl is getting her need for connection and oxytocin and bonding from her family, friends and boys without sex, right?

GURIAN: Half of our 17-year-olds have had sex. A hypothetical 17-year-old girl will have experimented with oral sex by now and may well have had intercourse. So I'm not naive, but what I'm teaching is her control of the process of giving this gift of this part of the self. And definitely, it's hard to make the case for this course of action if she's not getting love through the three families.

I'm more concerned with safe sex as a primary reason to practice these goals. She should set sexual goals that need to be met. Like being with someone for six months, maybe you could do intercourse; after three months, maybe oral sex. It's just like you set goals for anything in life you want to succeed at. That's what I preach; who knows if they'll do it. But I try to make the case.

When I tell groups of young people about the differences in male and female oxytocin, teen-aged girls just immediately go, "Ah-hah." That's a biochemical way I've found effective, to help them be self-controlling and self-aware.

A teen-age girl has got to know, this is what she's working with, and teen-age boys will take advantage of it. If a teen is on her own, she still should set those goals. And boys need to be accountable, of course, as well. They should set sexual and emotional goals too, and live up to them.

Pax provides an excellent analysis of the evolutionary advantages of human bonding and an intelligent discussion of how our biology -- and specifically oxytocin and vasopressin -- makes the intellectual choice of polyamory not so easy.

Polyamory sounds very utopian because it does away with the concept of jealousy, which has a lot of negative connotations, but the fact is that the same chemicals that produce jealousy produce the bonding effect that we think of as infatuation and love, which most people find pleasant. Most people can't have one without the other, and for most people you can't have sex without some oxytocin production, meaning bonding and jealousy will occur.

He discusses the differences in the level of bonding different people experience, and what that means for relationships. An especially interesting idea is that people should disclose their bondability when they begin relationships, just as they should their HIV status.

Sexual ethics means being up-front with those desires and expectations, in short being aware of the potiential for bonding and not betraying that. It also means being true to yourself. If you're the type of person that bonds easily, don't think you can live a sexually licentious life and not feel anxiety over it. If you're the type of person who just doesn't bond at all, understand that your partners may not be like you, and that you need to let them know before the opportunity for bonding occurs.

There is a bit of misinformation in his post, however. He says that oxytocin takes time to build up in a relationship.

Oxytocin takes time to build up. By having the relationship only last long enough to reach the sexual connection, then terminating it, the bonding formed is minimal.

Speak for yourself, dude! Because estrogen reinforces the effects of oxytocin, women can feel very bonded after a single night of sex.

Moreover, while it's certainly true that repeated interactions and sex can strengthen the bond, in men and women, this bond is not the result of the body's needing to reach a maximum level of endogenous oxytocin for it to take place. Instead, the combination of oxytocin and dopamine in the brain's reward center -- every time -- during orgasm trains the brain to prefer that person.

Still, I think Pax's post is well worth reading for its perceptive and sensitive ideas about how we can negotiate the differences in our neurochemistries.

I want to introduce you IndyScienceBlogs.org, an independent network of science-related blogs that I'm part of.

This was a self-organizing group effort and a very worthwhile experience. Our group's primary goal is to get a wider readership by making ourselves more findable and by taking advantage of the synergy of the group. At the same time, for me, it's been affirming to connect with other bloggers who, like me, are tracking scientific research out of deep personal interest.

The individual blogs and the main website have been in my blogroll for a while. In case you haven't checked them out, they are:

Emily DeVoto, a healthcare consultant who covers policy and news in The Antidote

Aleksandr Kavokin, a Russian M.D. with a special interest in unusual medical conditions in Rdoctor

Ed Minchau, an engineer whose fascination with robots is evident in Robot Guy

Sibin Mohan, a computer science doctoral student who blogs about everything from movies to religion to gadgets in Context Switch

Mike White, who brings his expertise in genomics and molecular biology to his posts about cutting-edge research in Adaptive Complexity

And The Beauty Brains, two anonymous cosmetic chemists who decode the mysteries of beauty products

Our group loves to pore through journals and research papers to find scientific information that may have been overlooked or too niche to be covered by newspapers and magazines. And we enjoy connecting, explaining and occasionally protesting.

You can subscribe to the group RSS feed for a daily smorgasbord of news and info on science and research. Every day, there's something surprising, exciting or weird going on in science. Don't miss it!

I reported a while back on studies showing that dogs had the same oxytocin response to petting and sweet interaction that their people did.

Occasionally, in a research paper, scientists insert a paragraph or two implying or downright asserting that animals have emotions that are very like ours. Biologists define emotions as physiological states, and neuroscience is increasingly able to map the brain activity that correlates with these states.

From out of left field -- a report on fMRI studies of women with severe spinal cord injuries by Rutgers researchers Barry Komisaruk and Beverly Whipple -- comes a statement that rodents experience brain activity during genital stimulation that is very similar to those of humans during orgasm. From the study:

Okay, why is this in a blog about oxytocin? Oxytocin is involved in empathy -- our ability to create mental models of the emotional states of others. Information frequently helps in this endeavor, as well.

I have often wondered about animal orgasm and whether by neutering our pets we deprive them of an important activity. In fact, when I had my first dog spayed, I asked the vet about this, and he suggested leaving one ovary. He did so, but she still didn't come into heat, so she didn't get to enjoy sexual intercourse.

I asked about tubal ligation for my second dog, and the vet said they didn't do it, it created too many health problems down the line. (Which was alarming, since this procedure is done on humans all the time.)

In any case, sex is likely at least as gratifying for animals as it is for humans.

The Belfast Telegraph reports on work done by a team of scientists who were the first to watch the brain in action during orgasm.

Barry R. Komisaruk, Carlos Beyer-Flores and Beverly Whipple scanned the brains of women with spinal cord injuries as they masturbated. It's been thought that because such injuries cut off feeling to the lower part of the body, these people would not be able to feel anything from sex, either.

(I'm not sure why doctors thought that, since there is plenty of anecdotal information about male paraplegics and quadriplegics being able to enjoy genital sex and ejaculation in the absence of feeling in the lower half of their bodies. Whatever.)

In any case, the scientists found that these women could orgasm -- and some of the women were thrilled to discover this as well, because they'd believed their doctors and had never tried masturbation or sex since their injuries.

The scans showed that orgasm involves many parts of the body and brain. In the brain, the reward and oxytocin systems were activated.

One part of the brain that was strongly activated was the nucleus accumbens,
which other scientists have shown becomes activated by psychoactive drugs
such as cocaine, nicotine and caffeine. Another two areas were the insula
and anterior cingulate, which become active in response to pain. "It
suggests there is some sort of inhibitory activity going on there, as orgasm
and vaginal stimulation are strong pain-blocking stimuli." The third
area of interest was the paraventricular nucleus, where the hormone oxytocin
is produced. Oxytocin is released into the blood stream at orgasm and causes
uterine contractions.

What is very interesting and new is that the scientists found an alternate neural pathway from the vagina and cervix to the brain: the vagus nerve. From the article:

the vagus nerve, which leads from the
lowest part of the brainstem, the medulla, through the base of the skull,
down the neck, into the chest cavity, through the diaphragm and into the
abdominal cavity without using the spinal cord. The first evidence that the
nerve goes to the pelvic region was found in 1990 with rats. At this stage,
however, it was not known whether it reached the same region in humans.

They do know that the vagus nerve is involved in feelings of satiety after eating. As the gut digests fat, it releases CKK, which travels up the vagus nerve to the brain, stimulating it to release oxytocin, which then travels back down the vagus nerve to tell the body it's had enough to eat.

This research, therefore, is another clue to the question of why people -- especially women -- eat when they're lonely. Eating activates the same neural pathways and oxytocin responses as sex.

This interview with Daniel Amen, author of the new book Sex on the Brain: 12 Lessons to Enhance Your Love Life," has some great tips on how to work on improving your sex life before you get into bed.

He also explains the differences in men's and women's oxytocin responses:

In women, holding hands, kind looks, doing something special for
someone our partner loves, are all ways to increase oxytocin. In turn,
it increases their bonding to their partner. For men, an orgasm
actually increases oxytocin, up to 500 percent. So men need orgasm to
become more bonded and connected, while women need touch and talking in
order to get to the place of wanting to help their partner have an
orgasm.

However, I don't believe he's quite correct. The brains of men, too, release oxytocin in social and intimate situations. That's why, in the trust studies done by Paul Zak and others, sniffing oxytocin increased trusting behavior. But men don't feel oxytocin's effects as strongly, nor do they last as long, because testosterone mutes oxytocin's effect, while estrogen increases it.

This story from Be the Best That You Can Be shows how much offering friendship and emotional support benefits the giver as well as the recipient.

Friendship Circle pairs teen-aged volunteers with kids who have special needs. They spend an hour or two a week hanging out. According to the story,

As one teen volunteer phrases it, "When I am with these children I feel
calm and soothed. I know there are no judgments being passed. I know
they don't care what I look like...together we live in the moment,
enjoying each second of each other's company".

That calm, soothed feeling comes from the release of oxytocin. When we engage in comforting, nurturing behavior, our brains release oxytocin. It's the same mechanism that releases oxytocin to a mother's body while she breastfeeds, but it's something anyone can enjoy.

According to John, Friendship Circle is a project of "the Chabad-Lubavitc, "a branch of Hasidic Judaism with a strong emphasis on emotional connection, community interaction, and the integration of good acts with spiritual observance."

This shows the way that spirituality can connect with the body to provide real-world experiences of joy.